Units Sensitive Relations

[dgschaefer]

We have to use multiple versions of Proe/Creo here but we maintain a common set of start parts / templates for all.  We've run into a problem with the "units sensitive" setting in our templates behaving differently in different versions.

In WF4, the settings is checked (as we want) in both the "initial" and "post regen" relations.  In WF5 & Creo2, however, it's turned off in the "post regen" section. This means, of course, that our M/P parameters with assigned units don't update properly in WF5 & Creo 2.

I wasn't aware that these could be set differently in the different areas of the relations dialog.  Based on the behavior I'm seeing, it seems that started in WF5. (It's a shame, but not surprising, that PTC didn't have it respect the settings that were in place. I did find the config option "relations_units_sensitive". Ironically, it defaults to yes, but say that "legacy relation data will not be unit sensitive until 'converted".)

I can fix it by opening my start parts in WF5 and saving them, but that means I need separate start parts for different WF4, something I don't want to do.

Is there any way I can force WF5 & up turn it on across the board without having to update it on a part by part basis?


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[dgschaefer]

Creo 2, M120

I have units sensitive relations turned on in my parts (in BOTH the initial & post-regen sections).  I need to report the volume of my part in fluid oz. and my part is in mmKsecC units.

I have the following relations set:

volume_gal = pro_mp_volume
volume_oz = volume_gal/128

The parameter "volume_gal" has the volume unit "gallons" set, the parameter "volume_oz" has no unit set.  Volume_gal reports a value of 0.429, but volume_oz reports 12707.026. The part volume is 1626499.395 mm^3, so the gallon conversion is correct, but Creo is dividing the raw volume by 128 instead of the gallons value.

How do I get Creo to divide correctly?

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[kimndave9]

It would be wrong anyway: Vol in ounces = Vol in gallons * 128

It looks like the software only uses the units to report. This means the volume is always in base units and is adjusted to display the converted number rather than scaling the value and using that.

Either it's a bug or a lousy way to meet a badly written software specification.

You can create your own units.

[dgschaefer]

Good catch, not that it changes anything.

The help files indicate this shouldn't happen in "About Units in Relations":

You can mix unitless parameters and parameters with units in the same relation. For example, if you have a unitless parameter A and parameter B with units, you can have a relation: d3=B*A. In this case, A is used as a scalar value. You can also include a unitless parameter and specify units directly in the relation. For example, d3=A[mm] + B.

Based on that last sentence, I tried these:

volume_oz = volume_gal[gal] * 128
volume_oz = pro_mp_volume [gal] * 128

Both generate errors, which I guess isn't surprising as that parameter isn't unitless.

KB doc CS121147 seems to indicate the opposite:


  *   Parameter created through a relation automatically get units assigned in Creo Parametric
  *   As soon as new parameters are created driven by the relations, they have units

However, I'm not seeing the parameter getting units assigned, just that the value is wrong.  I suppose it is being treated as though it has unit of mm^3.

The work around here is to convert directly from pro_mp_volume:

volume_oz = pro_mp_volume * .000033814022

It works, but not as tidy and won't work if the part's units are changed.

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[kimndave9]

Does the ounces parameter have units?

It's possible the software is ignorant enough that if it was also in gallons the calculation would work.

You know the units would be wrong, and I know the units would be wrong, but I'll bet a note on the drawing wouldn't care.

[dgschaefer]

It’s unitless.  I tried making it gallons; I then got a different, but still wrong, result.

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